Lapping machine



Dec. 28, 1937. 9 H. 5. m: 2,103,984

LAPPING MACHINE Filed Sept. 11, 1935 3 Sheets-Sheet l I I3 54' .J

HERBERT 5'. INDG'E W/T-Ess Dec. 28, 1937. H. s. INDGE 2,103,984

LAPPING MACHINE Filed Sept. 11, 1935 5 Sheets-Sheet 5 [l2 :5 :mIIIIIIIIIIIIA WITNESS 3 6 w, mmazxm Patented Dec. 28, 1937 um'rsoSTATES- LAPPING MACHINE Herbert S. Indge, Westboro, Mass, assignor toNorton Company, Worcester, Mesa, is corporation of MassachusettsApplication September 11, 1935, Serial No. 40,118

9 Claims.

This invention relates to lappingmachines, and more particularly to ahydraulically operated lapping machine. 1

One of the objects of this invention is to provide a simple, thoroughlypracticable, hydraulically operated lapping machine. Another object isto provide a hydraulically operated lapping machine which is arranged sothat hydraulic pressure may be equally distributed over the entireoperative surface of the lapping elements.

Another object of this invention is to provide a hydraulically operatedlapping machine in which the laps engage the work at apredeterminedpressure for a rough lapping operation and at a secondpredetermined pressure for a finish lapping operation.

Another object of this invention is to provide a hydraulically operatedpressure mechanism for a lapping operation, in which either a high or alow pressure may be obtained.

Another object is to provide a pressure control device in which a highora low pressure may be obtained or any desired pressure between thehigh and low. 1

Other objects will be in part obvious or in part pointed outhereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying'drawings, in which is shown one of the variouspossible embodiments of the mechanical features of this invention,

Fig. 1 is a side elevation of the improved lapping machine, having partsbroken away and shown in section to more clearly show the construction;

Fig. 2 is a diagrammatic showing of the hy draulic system;

Fig. 3 is a horizontal section, on an enlarged scale, takenapproximately on the line 33 of Fig. l;

Fig. 4 is a sectional view, partly in elevation, taken approximately onthe line 4-4-of Fig. 3;

Fig. 5 is a fragmentary vertical section taken approximately on the line5-5 of Fig. 4, showing the adjustable stop mechanism for the upper Fig.6 is a fragmentary cross sectional view, taken approximately on the line6-4: of Fig. 5, showing a top plan view of the movable stop member;-

- Fig. 7 is a vertical section, partly in elevation, on an enlargedscale, taken approximately on the line 'l'l of Fig. 5;

Fig. 8 is a fragmentary plan view, partlyin section, taken approximatelyon the line 8-8 of Fig. 7; I

Fig. 9 is a fragmentary cross sectional view, taken approximately on theline 9-9 of Fig. 4; and

Fig. 10 is a fragmentary vertical section, on an enlarged scale, showingthe counterbalance mechanism for the upper lap, taken approximately onthe line Ill-40 of Fig. 1.

Referring more particularly to the embodiment illustrated, the lappingmachine may be I constructed in its general aspects similar to thelapping machines illustrated in the prior U. S. patent to Indge No.1,870,328 dated August 9, 1932. This machine, as illustrated, maycomprise a base I0 which rotatably supports a lower lapping wheel II.The base I0 is provided with an upwardly extending column 12 having anoutwardly extending horizontal portion l3 which rotatably supports avertical spindle M. The spindle l4 carries a rotatable lapping wheel l5which is connected to the spindle H by means of a supporting plate l6.

Power may be obtained from any suitable source, such as an overheaddrive shaft or an electric motor mounted on the machine. For the sake ofillustration, a belt drive has been shown, comprising a driving beltwhich serves to ro-' tate a pulley 2|. The inner portion of the pulleyis formed as one part of a cone clutch. A slidable cone clutch member 22serves to cooperate to permit the power to be readily connected ordisconnected. The pulley 2| is rotatably supported on a horizontallyextending shaft 23 which is supported in bearings 24, 25, 26 and 21 inthe base HI. The clutch member 22 is slidably keyed to the shaft 23.When the clutch is in the full line position as indicated in Fig. 1, nopower is transmitted to the shaft 23. When it is desired to rotate theshaft 23, the cone clutch member 22 is moved toward the right, as viewedin Fig. 1, into engagement with the cone clutch member within the pulley2| so as to cause a rotation of the shaft 23. In order that the clutchmay be readily actuated from the operating position adjacent the frontof the machine, a pivotally mounted control lever 28 is supported on astud 29 on the base Ill. The lower end of the lever 28 is connected by apin 30 with a link 3| which is connected by means of a rod 32 supportedin bearings 33 and 34 with a yoked memher 35 and engages a groove 36 inthe hub 31 of the clutch member 22. By movement of the control lever 28in a counterclockwise direction, the clutch member 22 may be thrown intoengagement with the clutch member within the pulley 2i to cause arotation of the shaft 23, or when moved into the position illustrated infull line in Fig. 1, may disconnect the clutch and stop the rotationofthe shaft 23. A spring pressed roller 38 cooperating with an arrowpoint 39 on the yoked member 35 serves to hold the clutch either in orout of engagement.

In order that the shaft 23 may be stopped quickly when the clutch isdisengaged, a brake is provided comprising a brake disk 40 which isoperatively connected to the clutch member 22 and is arranged to engagea brake plate 4I mounted on the base of the machine.

The shaft 23 is provided with a worm which meshes with a Worm gear 46 onthe lower end of a vertical shaft 41. The shaft 4'I is connected by auniversal joint 48 with a shaft 49. The

' shaft 49 is preferably a telescopic shaft and is connected by auniversal joint 50 with a vertical shaft 5i supported in bearings 52 and53 in a bracket 54 mounted on the top of the column I2. The shaft 5I isprovided with a pulley 55 which is connected by belts 56 with a pulley51 which is mounted on a rotatable sleeve 58. The sleeve 58 is slidablykeyed by keys 59 to an upwardly extending projection 60 of the spindleI4, so

that when the clutch 22 is engaged, the vertical spindle I4 supportingthe upper lap I5 will be rotated.

The bracket 54 is adjustably mounted on the upper surface of the arm I2and is provided with a screw adjustment comprising a screw 62 which isrotatably'supported in a bracket 63 fixed to the column I2 and is screwthreaded into the bracket 54 so that the bracket 54 maybe adjustedtransversely of the machine to obtain the desired driving tension on thebelts 56.

The lower lap I1 is connected by a rotatable spider 65 and is rotated bymeans of a vertical sleeve (not shown). A work carrying cage 66 issupported above the lower lap II and is provided with a plurality ofwork receiving apertures for supporting a plurality of work pieces forsimultaneous lapping thereon. The work carrying cage is carried by thedriving pins or studs 61 and 68 and is carried through anirregularcombined rotary and planetary movement by a power driven gear mechanism,the details of which have not been illustrated in the present drawings,since this mechanism ,is not considered part of the present invention.For details of disclosure as to the means for rotating the lower lap IIand for rotating and gyrating the cage 66, reference may be had to theprior patents to Indge Nos. 1,610,527 dated December 14, 1926 and1,870,328 dated August 9, 1932.

The shaft 23 is provided with a worm I0 which meshes with a worm gear IImounted on a rotatable, vertically extending sleeve which is connectedwith spider 65 to rotate the lower lap II. The gears I5 and I6 areconnected in the manner illustrated in the prior Indge patents toproduce a predetermined movement of the work carrying cage 66. Fordetails of this mechanism, referencemay be had to the above-memtionedprior patents.

The spindle I4 which supports the upper lap 82 within the casing 83which is formed on the front end of the arm I3.

A counterbalance mechanism is provided to counterbalance the weight ofthe upper lap and its supporting mechanism. This mechanism comprises arack bar 85 fixed to the sleeve 82. The rack bar 85 meshes with a gear86 one. transversely extending shaft 81. The shaft 81 also supports asprocket 88 which is connected by a link chain 89 with a sprocket 90which is supported on a shaft M. I supported by an idler bracket 92which is pivotally mounted on a shaft 93. The idler bracket 92 is formedas a bell crank, one arm of which serves to support the shaft SI and theother arm of which is provided with an adjusting screw 94 which permitsadjusting the position of the bracket 92 so as to swing the sprocket 90and tension the link chain 89 as desired. The shaft 9I is also providedwith a sprocket 96. A link chain 9! wraps around the sprocket 96 andsupports at one endthereof an adjustable weight 98 which is of asuflicient size to counterbalance the weight of the upper lap and itsoperating mechanism. By utilizing the reduction gear mechanism betweenthe gear and link chain and sprocket mechanism-interposed between therack 85 and the weight 98, a two-to-one reduction is obtained so thatthe weight 98 need be only half the weight of the parts which arecounterbalanced, thus eliminating the necessity of a heavycounterbalance weight within the column I2. If desired, the shaft 87 maybe manually rotated by means of a Wrench or crank (not shown) to turngear 86 and move rack 85 to raise or lower the upper lap I5. v

In order to limit the downward movement of the upper lap I5, a suitablestop mechanism is provided to positively limit the downward movement ofthe lap so that it bears a definite and predetermined relation with thelower lap and the work. This stopcomprises an adjustable stop I00 whichis adjustably mounted in a bracket I0l which is fixed to the frame 83which supports the sleeve and spindle for the upper lap. The stop I00 isprovided with a screw threaded portion I02 meshing with a correspond-The shaft BI is in turn ingly threaded aperture within the bracket IOI.

A transversely extended clamping member I03 is adjustably mounted withinthe bracket IM and is provided with a threaded portion arranged toengage the threadsof the screw I02. The member I03 may be forced intoclamping relation with the screw I02 by means of a screw I04, so thatthe stop I00 may be adjusted into a predetermined position and thenlocked in fixed relation to the frame of the machine. A mov able stopscrew I06 is supported in a bracket I01 which is adjustably fixed to thesleeve,82. The sleeve 82 is provided with a plurality of threaded holesI08 so that the bracket I01 may be clamped in various positions on thesleeve 82 by means of screws I09 and H0. The stop screw I86 passesthrough a threaded. aperture III in the bracket I01 and is provided atits'upper end with a graduated micrometer adjusting end II2 whichenables a fine adjustment of the stop screw to vary the lower positionof the upper lap I5 as desired. In order that the stop screw I06 may belocked in adjusted position, the bracket I0! is preferably provided witha slot II4 which extends from the end of the bracket to the threadedaperture III. A clamping screw II5 extends transverse 1y through thebracket III! at a point intermediate the slotted area and serves tobindthe 75 bracket when desired to lock the screw I06 in a predeterminedadjusted position. By providing a plurality of threaded holes I in thesleeve 02, a quick adjustment of the bracket I01 may be obtained toadjust the stop in setting up the machine for lapping work pieces ofvarying thicknesses.

In order to obtain the desired lapping action between the opposed lapsII and I5 as the work is. carried through an irregular paththerebetween, it is essential to provide a pressure device to move thelaps relatively toward each other and to maintain them in operativeengagement with the plurality'of work pieces during the lappingoperation. In certain lapping operations, it is desirable tostart thelapping operation with a considerable amount of pressure between thelapping elements to cause a rough lapping of the work piece and to thenreduce the pressure for a finish lapping operation.

A fluid pressure system is provided to produce the desired operatingpressure on the upper lapping member. It is desirable to provide apressure device so that the pressure is uniformly applied to the upperlapping element so that the lapping surface thereof will remain parallelto the opposed lapping surface of the lower lap. In order to obtain thisresult, a pair of diametrically opposed fluid pressure cylinders I andI2I are mounted in brackets I22, I23, I24 and I25 which project fromdiametrice 'y opposite sides of the housing 83. The cylinders I20 andI2I are provided with pistons I26 and I21 re-' spectively. The pistonsI26 and I21 are con nected by piston rods I28 and I29 with a flangedplate I30 which is mounted on the lower end of the sleeve 82 and is heldin place thereon by means of a collar I3I. The piston rods I26 and I29are fixedly connected to the flanged plate I30 by means of nuts I32,I33,. I34 and I35 so that when the pistons I26 and I21 are moved withinthe cylinders I20 and I2I, the piston rods will cause a correspondingmovement to be transmitted to the vertically movabl, spindle I4 and theupper lap l5.

The flanged plate I30 is connected to the'lower end of the sleeve 82adjaxnt to the mounting I6 for the upper lap so that when pressure isapplied to the diametrically opposite pistons, the pressure is uniformlydistributed over the lapping surface and there is no tendency on thepart of the lap toassume other than a parallel relation with the opposedlapping surfaces, thus minimizing any errors in the lapping operationdue to any lost motionbetween the housing 83 and the sleeve 62.

Fluid for the pressure system is supplied from a reservoir :40 which ispreferably mounted within the base of the machine. Fluid is conveyedfrom the reservoir I40 through a pipe' MI by means of a gear pump I42which forces fluid through a. pipe I43 to a reversing or control valveI44. The valve I44 is of a balanced piston type comprising a valve stemI45 having valve pistons I46, I41 and I48 formed integrally therewith.The valve I44 is arranged to convey fluid in the position shown in Fig.2 through a pipe I 49 and pipes I50 and I5I into cylinder chambers I52and I53 to cause the pistons I26 and I21 to move into 'their extremeupward positions, as shown in Figs.

2 and 4, to separate the lap I5 from the lap II to permit loading andunloading of the work cage.

During the upward movement of the pistons I26 and I21, fluid isexhausted from cylinder chambers I54 and I55 through pipes I56 and I51through a pipe I50, through a valve chamber I59 between the valvepistons I41 and I48 and out through an exhaust pipe I60 into thereservoir I40. When the reversing valve I44 is shifted into the reverseposition, that is with the valve stem I45 moved downwardly (Fig. 2), thedirection of fluid from the pump I42 is reversed so that it passes intoa valve chamber I59 between valve pistons I41 and I40 and through pipeI58, and pipes I56 and I51 into cylinder chambers I54 and I55respectively to simultaneously move the pistons I26 and. H1 downwardlyto cause a downward movement of the sleeve 82 and spindle I4 to move theupper lap I5 into broken line position I5a. (Fig. 4) into lappingengagement with a plurality of work pieces I65.

In order that the valve I44 may be readily controlled from the operatingposition in front of the machine, a manually operable control lever I66is pivotally mounted on a stud I61. The stud I61 is also provided with alever I68 which is connected with the valve stem I45 by means of pinsI69. By moving the lever I66 from the full line position (Fig. 1) intodotted line position I06a, the valve I44 is retersed and fluid isadmitted to the upper cylinder chambers I54 and I55 to cause a downwardmovement of the upper lap I5. Similarly, when the lever I66 is movedfrom position I660, into full line position I66 (Fig. l), the valve ismoved into the position illustrated in Fig. 2 to admit fluid underpressure to the lower cylinder chambers I52 and I53 so as to raise theupper lap I5 to permit removal of the work which has been lapped andpermit insertion of new pieces of work. I

In order to attain the main object of this invention, it is desirable toprovide a pressure controlling mechanism so that the fluid pressureapried to th. upper cylinder chambers I54 and I55 will cause the upperlap I5 to bear against the work pieces at a desired predeterminedpressure for either a rough or a finish lapping operation. Asillustrated in the drawings, this is accomplished by providing avariable pressure regulating valve I10. This valve is connected by apipe I" with the pressure pipe I43. The valve I10 may be adjusted bymeans of an adjusting screw I12 so that if the pressure supplied by thepump I42 exceeds the desired pressure, a valve member I13 will be raisedfrom its seat against the tension of a spring I14 and allow the excessfluid under pressure to exhaust through a pipe I15 into the reservoir.

In the lapping of certain types of work,it is I desirable to provide apressure controlling mechanism which enables the lapping operation to bestarted with the lapping elements pressing upon the work at asubstantial predetermined pressure to initially lap the work pieces andto then change the pressure to produce a final or finish lappingoperation. This is preferably accomplished by providing a secondpressure regulating valve I which is connected by a pipe I8I with thepipe I43. This valve is identical with the pressure regulating valve I10and comprises a movable member I82 which is held against its seat bymeans of a spring I83 the tension of which may be adjusted by anadjusting screw I84. In setting up the machine, the pressure regulatingvalve I10 is adjusted to give the predetermined maximum pressure desiredupon the upper lap, and the pressure regulating valve I80 is adjustedfor the predetermined minimum pressure. During the normal use of themechanism may proceed to the desired extent. desired to reduce thepressure to a finish lapping above described, the fluid pressure systemis so operated that any pressure in excess of the low pressure to whichthe valve I80 is set would cause the valve member I82 to rise from itsseat and allow excess fluid under pressure to exhaust through a pipe-I85 into the reservoir.

In order that either a high or a low pressure may be applied to theupper lapping elements, a valve I90 is inserted within the pipe I8I.'This valve is arranged so that in the position illustrated in Fig. 2,fluid under pressure is out 01f from the regulating valve I80, thusrendering the low pressure regulating valve I80 inoperative so that theupper lap will be maintained in lapping engagement with the work at thehigher pressure to which the Valve I10 is set. In this position of theparts, the rough lapping operation When it is pressure, the valve I90 isturned through 90 to allow fluid under pressure to pass through pipe I8Iinto valve I80, thus rendering the low pressure regulating valve I80operative so that if the pressure from the pump I42 exceeds the lowpressure desired for the finish lapping operation, the valve member I82opens and allows the excess fluid under pressure to exhaust through thepipe I85.

It will be readily apparent from this disclosure that by manipulation ofthe valve I90, that is opening the valve to a greater or lesser extent,practically any pressure between the high and the low pressure to whichvalves I10 and I80 have been set may be obtained.

In lapping certain types of work, such as thin objects which are readilydistorted, it may be desirable to start the lapping operation with acomparatively light pressure of the laps on the work to remove anyirregularities or high spots on the surfaces to be lapped and to thenincrease the pressure to lap the work to the approximate size and finishand then'to reduce the pressure to a light or final finishing pressurefor the final lapping on the work piece. This may be accomplishedbyopening the valve I90 and allowing the low pressure regulating valve I80to be operative during the initial operation so that the laps willengage the work for an initial lapping operation and to then close thevalve I90 and allow the valve I99 to cause the laps to engage the workat a higher pressure for lapping the surfaces of the work to therequired'extent. Then a final or finish lapping is obtained by againopening the valve I90 to render the low pressure valve I80 operative soas to reduce the pressure of the laps on the work during the final orfinish lapping operation.

In order to facilitate adjustment of the pressure regulating valves I10and I80, a pressure indicating gauge I95 is connected in pipe line I43by means of a pipe I96 so that in setting the high pressure valve I10with valve I90 closed, an indicating control valve I91 may be opened topermitthe operator to observe a visible indication of the pressurewithin the systemwhile adjusting the screw I12 of valve I10. After valveI10 has been set to the desired pressure; the valve I90 may be opened torender the valve I operative and the adjusting screw I84 may be adjustedso that the release valve I80 will give the desired finish lappingpressure on the upper lap.

In the operation of this machine, the work pieces I65 are inserted inthe work receiving apertures within the cage 66, the control lever 28 isthen moved in a counterclockwise direction (Fig. 1) to engage the clutch22 and rotate the shaft 23 which through connecting mechanism causes thelower lap II and the upper lap I5 as well as the cage 66 to beset inmotion. The operator then moves the lever I66 from the full lineposition into the broken line position I56a. (Figs. 1 and 4) whichserves to move the stem I45 of the valve I44 downwardly from the fullline position illustrated in Fig. 2 to the dotted line position so as toadmit fluid under pressure through pipe I58 simultaneously into theupper cylinder chambers I54 and I55 to cause the upper lap I5 to moveinto lapping engagement with the work pieces. Assuming the pressureregulating valves I10 and I80 to have been previously set to the desiredpressures, the lap I5 in the position of the parts illustrated in Fig. 2is moved into lapping engagement with the work at a pressure governed bythe high pressure valve I10 to cause a rough fast lapping of the workpiece. After the preliminary or initial lapping has been carried on to apredetermined extent, the valve I is shifted to admit fluid underpressure through pipe IIlI so as to render the pressure regulating valveI80 operative, thereafter allowing the valve I80 to control the pressureapplied to the upper lap to permit a' final or finish lapping operationfor a predetermined period. After the lapping operation has beencompleted to the desired extent, the control lever I66 is raised fromthe position I650. into the full line position, causing the valve stemI45 to move into the full line position, as illustrated in Fig. 2, so asto admit fluid under pressure through the pipe I49 simultaneously intocylinder chambers I52 and I53 to cause the upper lap to move out ofengagement with the work and into an inoperative position.

It will thus be seen that there has been provided by this inventionapparatus in which the various objects hereinabove set forth togetherwith may thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not in alimiting sense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A lapping machine comprising a base, a rotatable lap supported onsaid base, an opposed rotatable lap, a rotatable spindle to support saidsecond lap, means to rotate said spindle, means including a sleeve tosupport said spindle, means including a pair of fluid pressure pistonsand cylinders arranged on diametrically opposite sides of said spindle,a pair of piston rods connected with each of said pistons, a mountingfor said second lap on the lower end of said spindle which is adjacentto the end of the sleeve, and rigid connections between the lower end ofsaid sleeve and the piston rods which are arranged so that when fluidunder pressure is admitted to said cylinder, the pressure will bedistributed substantially equally over the entire surface of the lap.

2. A lapping machine of the type having a base, a pair of opposed,relatively rotatable lapping elements. and a work carrying cage arrangedtherebetween for supporting a plurality of work pieces for asimultaneous lapping operation between said laps, a rotatable spindle tosupport one of said laps, bearings for said spindle,

a sleeve to support said bearings, a counterbalance weight tocounterbalance the weight of said movable parts, an adjustablemicrometer stop screw to positively limit the movement of said movablelap toward and from the other, a pair of fluid pressure cylinders whichare fixed to the base and arranged on diametrically opposite sides ofsaid spindle and sleeve, pistons within said cylinders, a control valveto control the admission and exhaust of fluid from said cylinders,piston rods connected to said pistons respectively and extending beyondsaid cylinders, and con nections between said piston rods and the lowerend of said sleeve which are located adjacent to the movable lapmounting which serve to distribute a substantially equal pressure overthe entire lapping surface.

3. A lapping machine of the type having a pair of opposed relativelyrotatable lapping elements one of which is movable relatively toward andfrom the other and a work cage therebetween for simultaneouslysupporting a plurality of work pieces for a simultaneous lapping actionbetween the operative faces of-said lapping elements, a rotatablespindle rigidly to support said movable lapping element, a movablesleeve rotatably to support said spindle, and means to cause a relativeapproaching and receding movement between said lapping elementscomprising a plurality of spaced fluid pressure cylinders arrangedsymmetrically with respect to the axis of said movable lapping element,pistons within said cylinders, connections between the pistons andmovable sleeve which are located adjacent to said movable lappingelement, and means including a control valve which is operativelyconnected to admit fluid under pressure simultaneously to either end ofsaid cylinders to cause a relative approaching or receding movementbetween said lapping elements and to maintain said elements in lappingengagement with the work at a predetermined positive pressure.

from the other and'a work cage therebetween forsimultaneously supportinga plurality of work pieces for a simultaneous lapping action between theopposed faces of said lappingelements, a rotatable spindle rigidly tosupport said movable lapping element, a movable sleeve rotatably tosupport said spindle, and means to cause a relative approaching andreceding movement between said laps comprising a pair of spaced fluidpressure cylinders fixed on diametrically opposed sides of the axis ofsaid movable lapping element, pistons within said cylinders, connectionsbetween the pistons and movable sleeve which are adjacent to saidlapping element, and means including a control valve which isoperatively connected to admit fluid under pressure simulta neously toeither end of said cylinders to cause a relative approaching or recedingmovement between said lapping elements to maintain said elements inengagement with the work at a predetermined positive pressure.

5. A lapping machine of the type having a pair of opposed rotatablelapping elements which are movable relatively toward and from each otherand a work carrying cage therebetween arranged to carry a plurality ofwork pieces through an irregular path between the operative faces ofsaid laps, a fluid pressure system including a piston and cylinder whichare arranged to cause a relative approaching or receding movementbetween said lapping elements, a control valve to convey fluid underpressure to eitherend of said cylinder, means including a fluid pumpand. a pipe to tain the laps in engagement with the work at a secondpredetermined positive pressure for a fin ish lapping operation, andmeans including a valve between the pipe and said second pressureregulating valve to render said second pressure regulating valveinoperative during the rough lapping operation.

6. A lapping machine of the type having a pair of .opposed rotatablelapping elements one of which is movable relatively toward and from theother, a work carrying cage therebetween for simultaneously supporting aplurality of work pieces for a simultaneous lapping action between theopposed faces of said laps, a rotatable spindle rigidly to support oneof said laps, an axially movable sleeve rotatably to support saidspindle, andmeans comprising a pair of spaced fluid pressure cylindersarranged on diametrically opposite sides of the axis of the movable lap,pistons within said cylinders which are operatively connected to the endof said sleeve adjacent to said lap to cause a relative approaching andreceding movement between the laps, a control valve arrangedsimultaneously to admit fluid under pressure to either end of saidcylinders, means including a fluid pump and pipe which are operativelyconnected to convey fluid under pressure to said control valve andcylinders, a pressure regulating valve in said pipe which is arranged toregulate the pressure of the fluid so as to cause the laps to bemaintained in engagement with the work at a predetermined positivepressure for an initial lapping operation, a second pressure regulatingvalve in said pipe line which is connected in series with said firstpressure regulating valve to maintain the laps in lapping engagementwith the work at a second predetermined positive pressure for a finishlapping operation which is inoperative during the initial lappingoperation, and means including, a stop valve to render said secondpressure regulating valve operative after a predetermined initiallapping operation.

7. A lapping machine of the type having a pair of opposed relativelyrotatable lapping elements one of which is movable relatively toward andfrom the other and a work carrying cage therebetween arranged to carry awork piece through an irregular path between the operative faces of saidlaps, a fluid pressure system including a piston and cylinder which arearranged to cause a relative approaching or receding movement betweensaid lapping elements, a control valve to convey fluid under pressureto'either end of saideration, and means including a valve locatedbetween the pipe and said second pressure regulating valve by which anypositive pressure between the maximum and minimum of the two pressureregulating valves may be obtained.

8. A lapping machine of the type having a pair of opposed rotatablelapping elements which are movable relatively toward and from each otherand a work carrying cage therebetween arranged to carry a plurality ofwork pieces through an irregular path between the operative faces ofsaid laps, a fluid pressure system including a piston and cylinder whichare arranged to cause a relative approach and receding movement betweensaid lapping elements, a control valve to convey fluid under pressure toeither end of said cylinder, means including a fluid pump and pipe toconvey fluid to said valve and cylinder, a pressure regulating valve insaid pipe line which is arranged to be set for a maximum pressurebetween said lapping eiements and the work, a second pressure regulatingvalve in said pipe which is connected in series with the first pressureregulating valve and arranged to be adjusted for a minimum pressurebetween said lapping elements and work, and means including a manuallyoperable valve operatively connected with said second pressureregulating valve and pipe whereby any positive pressure may be obtainedbetween the said minimum and maxlmum pressures.

9. A lapping machine of the type having a pair of opposed relativelyrotatable lapping elements one of which is movable relatively toward andfrom the other and a work carrying cage therebetween arranged to carry'aplurality of work pieces through an irregular path between the operativefaces of said laps, a rotatable spindle rigidly to support one of saidlaps, a movable sleeverotatably supporting said spindle, a fluidpressure system including a piston and cylinder which are operativelyconnected to move said sleeve and cause a relative approaching andreceding movement between said lapping elements, a control valve toconvey fluid under pressure to either end of said cylinder, meansincluding a fluid pressure pump and pipe to convey fluid to said valveand cylinder, a pressure regulating valve in said pipe which is arrangedto maintain said laps in engagement with the work at a maximum positivepressure, a second pressure regulating valve in said pipe which isconnected in series with the first pressure regulating valve to maintainsaid laps in engagement with the work at a minimum predeterminedpositive pressure, and means including a valve between said pipe andsaid second pressure: regulating valve whereby the pressure between saidlapping elements may be adjusted to produce any pressure between theminimum and maximum pressures of said pressure regulating valves.

HERBERT S. INDGE.

